The invention relates generally to superconducting homopolar inductor alternators, and more particularly to a technique for shielding a superconducting field coil within a homopolar inductor alternator against electro-magnetic (EM) fields.
A superconducting homopolar inductor alternator (HIA) utilizes a stationary superconducting field winding located between the rotor and the stator. The field winding is therefore exposed to alternating EM fields that result in eddy current and hysteresis losses. Excessive heating generated in a superconductor as a result of induced eddy currents and hysteresis currents can overheat, quench the superconductor, and shut down the electrical machine. Since all thermal losses in the superconductor must be removed by cryogenic refrigeration, a poorly shielded field winding would significantly increase the capacity and cost of the cryorefrigerator.
Typical HIA machines utilize resistive field windings that are designed to dissipate all the ohmic heating caused by the eddy currents, undesirably resulting in significantly lower machine efficiency.
It would be advantageous to provide a technique for shielding a superconducting field coil within a homopolar inductor alternator against electro-magnetic (EM) fields that overcomes the disadvantages described above associated with typical HIA machines.